如何分析Thread dump

• 新建状态（New）

用new语句创建的线程处于新建状态，此时它和其他Java对象一样，仅仅在堆区中被分配了内存。

• 就绪状态（Runnable）

当一个线程对象创建后，其他线程调用它的start()方法，该线程就进入就绪状态，Java虚拟机会为它创建方法调用栈和程序计数器。处于这个状态的线程位于可运行池中，等待获得CPU的使用权。

• 运行状态（Running）

处于这个状态的线程占用CPU，执行程序代码。只有处于就绪状态的线程才有机会转到运行状态。

• 阻塞状态（Blocked）

阻塞状态是指线程因为某些原因放弃CPU，暂时停止运行。当线程处于阻塞状态时，Java虚拟机不会给线程分配CPU。直到线程重新进入就绪状态，它才有机会转到运行状态。

阻塞状态可分为以下3种：

① 位于对象等待池中的阻塞状态（Blocked in object’s wait pool）：当线程处于运行状态时，如果执行了某个对象的wait()方法，Java虚拟机就会把线程放到这个对象的等待池中，这涉及到“线程通信”的内容。

② 位于对象锁池中的阻塞状态（Blocked in object’s lock pool）：当线程处于运行状态时，试图获得某个对象的同步锁时，如果该对象的同步锁已经被其他线程占用，Java虚拟机就会把这个线程放到这个对象的锁池中，这涉及到“线程同步”的内容。

③ 其他阻塞状态（Otherwise Blocked）：当前线程执行了sleep()方法，或者调用了其他线程的join()方法，或者发出了I/O请求时，就会进入这个状态。

• 死亡状态（Dead）

当线程退出run()方法时，就进入死亡状态，该线程结束生命周期。

我们运行之前的那个死锁代码SimpleDeadLock.java，然后尝试输出信息(/这是注释，作者自己加的/)：

/* 时间，jvm信息 */
2017-11-01 17:36:28
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.144-b01 mixed mode):
 
/* 线程名称：DestroyJavaVM
编号：#13
优先级：5
系统优先级：0
jvm内部线程id：0x0000000001c88800
对应系统线程id（NativeThread ID）：0x1c18
线程状态： waiting on condition [0x0000000000000000]  （等待某个条件）
线程详细状态：java.lang.Thread.State: RUNNABLE  及之后所有*/
"DestroyJavaVM" #13 prio=5 os_prio=0 tid=0x0000000001c88800 nid=0x1c18 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"Thread-1" #12 prio=5 os_prio=0 tid=0x0000000018d49000 nid=0x17b8 waiting for monitor entry [0x0000000019d7f000]
/* 线程状态：阻塞（在对象同步上）
    代码位置：at com.leo.interview.SimpleDeadLock$B.run(SimpleDeadLock.java:56)
    等待锁：0x00000000d629b4d8 
    已经获得锁：0x00000000d629b4e8*/
   java.lang.Thread.State: BLOCKED (on object monitor)
    at com.leo.interview.SimpleDeadLock$B.run(SimpleDeadLock.java:56)
    - waiting to lock <0x00000000d629b4d8> (a java.lang.Object)
    - locked <0x00000000d629b4e8> (a java.lang.Object)
 
"Thread-0" #11 prio=5 os_prio=0 tid=0x0000000018d44000 nid=0x1ebc waiting for monitor entry [0x000000001907f000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at com.leo.interview.SimpleDeadLock$A.run(SimpleDeadLock.java:34)
    - waiting to lock <0x00000000d629b4e8> (a java.lang.Object)
    - locked <0x00000000d629b4d8> (a java.lang.Object)
 
"Service Thread" #10 daemon prio=9 os_prio=0 tid=0x0000000018ca5000 nid=0x1264 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"C1 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x0000000018c46000 nid=0xb8c waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x0000000018be4800 nid=0x1db4 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x0000000018be3800 nid=0x810 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x0000000018bcc800 nid=0x1c24 runnable [0x00000000193ce000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:171)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
    - locked <0x00000000d632b928> (a java.io.InputStreamReader)
    at java.io.InputStreamReader.read(InputStreamReader.java:184)
    at java.io.BufferedReader.fill(BufferedReader.java:161)
    at java.io.BufferedReader.readLine(BufferedReader.java:324)
    - locked <0x00000000d632b928> (a java.io.InputStreamReader)
    at java.io.BufferedReader.readLine(BufferedReader.java:389)
    at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)
 
"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x0000000017781800 nid=0x524 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001778f800 nid=0x1b08 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
 
"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000000001776a800 nid=0xdac in Object.wait() [0x0000000018b6f000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000d6108ec8> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
    - locked <0x00000000d6108ec8> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
 
"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000017723800 nid=0x1670 in Object.wait() [0x00000000189ef000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000d6106b68> (a java.lang.ref.Reference$Lock)
    at java.lang.Object.wait(Object.java:502)
    at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
    - locked <0x00000000d6106b68> (a java.lang.ref.Reference$Lock)
    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
 
"VM Thread" os_prio=2 tid=0x000000001771b800 nid=0x604 runnable 
 
"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000001c9d800 nid=0x9f0 runnable 
 
"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000001c9f000 nid=0x154c runnable 
 
"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000001ca0800 nid=0xcd0 runnable 
 
"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000001ca2000 nid=0x1e58 runnable 
 
"VM Periodic Task Thread" os_prio=2 tid=0x0000000018c5a000 nid=0x1b58 waiting on condition 
 
JNI global references: 33
 
 
/* 此处可以看待死锁的相关信息！ */
Found one Java-level deadlock:
=============================
"Thread-1":
  waiting to lock monitor 0x0000000017729fc8 (object 0x00000000d629b4d8, a java.lang.Object),
  which is held by "Thread-0"
"Thread-0":
  waiting to lock monitor 0x0000000017727738 (object 0x00000000d629b4e8, a java.lang.Object),
  which is held by "Thread-1"
 
Java stack information for the threads listed above:
===================================================
"Thread-1":
    at com.leo.interview.SimpleDeadLock$B.run(SimpleDeadLock.java:56)
    - waiting to lock <0x00000000d629b4d8> (a java.lang.Object)
    - locked <0x00000000d629b4e8> (a java.lang.Object)
"Thread-0":
    at com.leo.interview.SimpleDeadLock$A.run(SimpleDeadLock.java:34)
    - waiting to lock <0x00000000d629b4e8> (a java.lang.Object)
    - locked <0x00000000d629b4d8> (a java.lang.Object)
 
Found 1 deadlock.
 
/* 内存使用状况，详情得看JVM方面的书 */
Heap
 PSYoungGen      total 37888K, used 4590K [0x00000000d6100000, 0x00000000d8b00000, 0x0000000100000000)
  eden space 32768K, 14% used [0x00000000d6100000,0x00000000d657b968,0x00000000d8100000)
  from space 5120K, 0% used [0x00000000d8600000,0x00000000d8600000,0x00000000d8b00000)
  to   space 5120K, 0% used [0x00000000d8100000,0x00000000d8100000,0x00000000d8600000)
 ParOldGen       total 86016K, used 0K [0x0000000082200000, 0x0000000087600000, 0x00000000d6100000)
  object space 86016K, 0% used [0x0000000082200000,0x0000000082200000,0x0000000087600000)
 Metaspace       used 3474K, capacity 4500K, committed 4864K, reserved 1056768K
  class space    used 382K, capacity 388K, committed 512K, reserved 1048576K